The present invention relates to cementing operations and, more particularly, to extended cement compositions comprising cement, water, oil-swellable particles, and a set retarding additive and associated methods of use.
Cement compositions are commonly utilized in subterranean operations, particularly subterranean well construction and remedial operations. For example, in subterranean well construction, a pipe string (e.g., casing, liners, etc.) may be introduced into the well and cemented in place. The process of cementing the pipe string in place is commonly referred to as “primary cementing.” In a typical primary cementing operation, a cement composition may be pumped into an annulus between the walls of a well bore and the exterior surface of the pipe string disposed therein. The cement composition sets in the annular space, thereby forming an annular sheath of hardened, substantially impermeable cement that supports and positions the pipe string in the well bore and bonds the exterior surface of the pipe string to the walls of the well bore. Among other things, the annular sheath of set cement surrounding the pipe string functions to prevent the migration of fluids in the annulus, as well as protecting the pipe string from corrosion. Cement compositions also may be used in remedial cementing operations, such as squeeze cementing and the placement of cement plugs.
Once set, the cement sheath may be subjected to a variety of cyclic, shear, tensile, impact, flexural, and/or compressive stresses that may lead to failure of the cement sheath. Such failure may be the result of fractures, cracks, and/or debonding of the cement sheath from the pipe string and/or the formation. Undesirably, cement-sheath failure may lead to loss of zonal isolation, resulting, for example, in the undesirable migration of fluids between formation zones. This may lead to undesirable consequences such as lost production, costly remedial operations, environmental pollution, hazardous rig operations resulting from unexpected fluid flow from the formation caused by the loss of zonal isolation, and/or hazardous production operations. Furthermore, failure of the cement sheath also may be caused by forces exerted by shifts in subterranean formations surrounding the well bore, cement erosion, and repeated impacts from the drill bit and the drill pipe.
In certain applications, extended cement compositions may be used. As used herein, the term “extended cement composition” refers to a cement composition capable of remaining in a pumpable fluid state for an extended period of time (e.g., at least about 1 day). A fluid is considered to be in a pumpable fluid state where the fluid has a viscosity of less than 70 Bc, as measured using an FANN Atmospheric Consistometer Model 165AT (available from FANN Instrument Company, Houston, Tex.) at room temperature (for example, 78° F.). In general, the extended cement compositions comprise cement, water, and a set retarder and remain in a pumpable fluid state for an extended period of time. When desired for use, the extended cement composition should be capable of being activated whereby reasonable compressive strengths are developed. For example, a cement set accelerator may be added to the extended cement composition whereby the composition sets into a hardened mass. Among other things, the extended cement compositions may be suitable for use in well bore applications, for example, where it is desired to prepare the cement composition in advance. This may allow, for example, the cement composition to be stored prior to its use. In addition, this may allow, for example, the cement composition to be prepared at a convenient location and then transported to the job site for use. Accordingly, capital expenditures associated with the cementing operations may be reduced due to a reduction in the need for on-site bulk storage and mixing equipment.